The first thing Brian H noticed was that he could grow a real beard. It had been years since that had been possible. Brian, 34, suffers from alopecia areata, an autoimmune disease afflicting about 1 per cent of men and women, causing hair to fall out, often all over the body.

After trying various treatments, Brian enrolled this year in a study at Columbia University Medical Center testing whether a drug approved for a bone marrow disorder could help people with alopecia. One of the study’s leaders, Angela Christiano, is a dermatology professor and geneticist who herself has alopecia areata.

After successfully testing on mice two drugs from a new class of medicines called JAK inhibitors, which suppress immune system activity by blocking certain enzymes, the researchers began testing one of the drugs, ruxolitinib, on seven women and five men. Some of their findings were published Sunday in the journal Nature Medicine.

The results for Brian and several other participants have been significant.

“Pretty quickly, there were sort of fringes,” Brian said. Then “three or four large areas started to show hair growth”, and by five months, he had plenty of hair on his head, arms, and even his back. “I was blown away,” he said.

The disease differs from other types of hair loss, including male pattern baldness, and there is no evidence the drug will work for those conditions. Experts caution that even for alopecia areata, it is too early to know if the treatment will work for most patients and if there are significant side effects or safety concerns.

The study is continuing, but so far a few participants did not regrow hair, said Dr Julian Mackay-Wiggan, director of Columbia’s dermatology clinical research unit and an author of the study.

“It appears to work — not in everyone, but in the majority,” she said. “We need a lot more data on the long-term risks in healthy individuals. But it’s certainly very exciting in terms of hair growth. It was surprising how quickly and impressively the growth occurred.”

But Dr George Cotsarelis, a dermatologist at the University of Pennsylvania, urged caution until further research is conducted. He said it makes sense that drugs suppressing immune system activity would work for a disorder caused by an overly active immune reaction.

But because patients in the study received twice-daily pills that circulated ruxolitinib in their bodies, rather than topical cream, he said they were “treated systemically with a